DarwinKoala: If I might be forgiven for discussing some Camelot history....

You had a valid historical reason for wondering if being reduced to one piece constitutes a loss.  The current (World Camelot Federation) rule that governs, though, is:

The game is won if a player captures all of his opponent's pieces, and has two or more of his own pieces left.

This rule clarifies the question of whether two or more vs. one is a win.  It is not a win; its outcome, possibly a draw, is yet to be determined.  In the 1930 rules, and in the initial editions of the 1931 rules, a win by elimination required the elimination of all of the opponent’s pieces.  In later 1931 editions, however, the wording was changed to “elimination of all, or all but one, of the opponent’s pieces.”  This change in wording resulted from the fact that it is not possible for one piece to stop another (opposing) piece from entering its Castle.  Thus, if one side has two pieces and the other side one piece, it is impossible (with normal play) for the one to stop the two, even if the stronger side already has one of its pieces in the opponent’s Castle, and even if the weaker side temporarily has the opposition (a position where the pieces are on the same rank, file, or diagonal with an odd number of squares separating them, and the stronger side must move, thereby allowing the weaker side to stop the advance of the stronger side’s piece).  This change in wording, however, not only failed to take into account possible misplays by the stronger side; much more importantly, it failed to take into account situations where the weaker side could initiate a combination (a series of forced moves that leads to a significant change in positional or material advantage) that would, although reducing itself to one piece, reduce the stronger opposing side to one piece or no pieces, thus securing a draw.

So, when you're reduced to one piece you haven't lost yet.

Hope this helps!